[ICOM] Icom 706MKIIG vs Yaesu FT450

[Jim Hargrave]

Dave,

You can eliminate a lot of the spikes, etc by running a heavy battery cable
direct from the battery to the radio. The battery has a great leveling
effect on spikes and ignition noise. I never connect a transmitter to any of
the accessory circuits for that reason. In my Motorhome, I have a #10
stranded wire pair going direct from the IC-735 to the coach battery. Noise
and voltage spikes are almost non-existent in this setup. Another trick is
to wrap several turns of the power wire around a large ferrite core as close
to the radio as you can get.

The only real noise source in most RV's is the battery charger that operates
when the power unit is running or the RV is plugged into an external AC
power source. This charger is a typical RV converter that furnishes 12 Volt
to the lighting and charges the house battery. Most of them use a pulser
circuit with SCR's. This problem can be solved by turning off the charger
when operating the radio and using a normal linear charger. Most of these
can be converted to a linear charger and it will eliminate this source of
noise. All of the 12 volt runs make a great antenna and it sounds like an
old spark gap transmitter across the entire HF spectrum. Now that is a real
"noise floor" that is not the radio fault. Some of the high end inverters
are now incorporating switching chargers that are a lot quieter.

   * 73's Jim W5IFP *


   >-----Original Message-----
   >From: icom-bounces at mailman.qth.net
   >[mailto:icom-bounces at mailman.qth.net]On Behalf Of Dave Shirk
   >Sent: Sunday, May 18, 2008 4:37 AM
   >To: ICOM Reflector
   >Subject: Re: [ICOM] Icom 706MKIIG vs Yaesu FT450
   >
   >
   >Jim,
   >
   >I like the old 735 as well (my main rig is the 7000 which I love). I
   >am in the long process of getting it back operational with much great
   >help from Kevin, K8SU. It seems Icom used several 10mF tantalum caps
   >in the rig which have 16 volt ratings. Between age, and spikes from
   >alternators in a mobile environment, I am finding several bad ones.
   >Kevin pointed out the first one to check, and it indeed was shorted
   >(it made the entire radio after the power switch a short to ground on
   >the 13.6V power input). Without his input, I would have given up
   >trying to find it.
   >
   >I am posting this to let others know that if you have old 735's which
   >you still want to use but are not functional (in receive or a shorted
   >to ground), pull them out and replace about one to two dollars worth
   >of parts. The second bad cap I found caused a 1 ohm resistor to become
   >a 400 ohm resistor and also blow a transistor. I am waiting for more
   >parts to arrive, but look forward to getting the 735 back on the air
   >as a back up and haul around rig.
   >
   >And again, a big public thanks to Kevin, K8SU.
   >
   >73 - Dave - KI4KQ
   >
   >On May 17, 2008, at 2:02 PM, Jim Hargrave wrote:
   >
   >> I still prefer my IC-735 and fortunately I have room for it in the
   >> Motorhome.  I may be a little partial to Icom because of the
   >> reliability
   >> that I have had with the 735 for the 22 years that I have owned it.
   >> On the
   >> flip side my Yaesu FT-920 fits very nicely in my home operating
   >> desk. I
   >> think its among the nicest radios Yaesu has built. So I basically
   >> support
   >> both brands. Each has its Pros and Cons.
   >>
   >>   * 73's Jim W5IFP *
   >
   >----
   >Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
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   >